1. Field of the Invention
The present invention pertains to the art of cooking and, more particularly, to field calibrating a microwave oven voltage switch point.
2. Discussion of the Prior Art
As widely known in the art, a microwave employs a magnetron to generate microwaves which are directed into an oven cavity for cooking purposes. The magnetron operates based on a high voltage received from a transformer that is connected to a line voltage. Microwave controls that are configured to run on two different line voltages are typically designed to automatically measure the line voltage in order to determine a particular tap associated with the power supply transformer which should be used. This automatic arrangement therefore sets the appropriate tap before a cooking cycle is initiated. By way of example, a microwave oven may be supplied with a nominal line voltage of 208 or 240 VAC, with this voltage being stepped up by the transformer in order to power the magnetron. Preferably, the supply power would be maintained substantially constant. However, the actual line voltage can vary over a tolerance range which may be in the order of +/−10-15%.
With this in mind, proper operation of the microwave oven requires that the appropriate tap be selected. Unfortunately, the voltage measurement taken by the microwave oven is limited in accuracy, mainly based on component tolerances and operational variances over time. Certainly, the voltage measurement can be tested and set within a couple of volts when it leaves a manufacturing factory, but the measurement can drift over time. If the oven is placed in use after being shipped from the factory and there is no way for a service technician to correct the calibration once it is drifted, unnecessary failures can occur.